我为ado.net设计了小型存储库模式。现在我无法以正确的方式处理异常。如果发生任何问题，我想将错误推送到调用环境。如果没有错误发生，那么结果集将被推送到调用环境。
我有一个名为AdoRepository的存储库，它扩展了其他存储库类，如employee等。我们从mvc控制器调用employee repository function。所以如果在数据获取期间发生任何错误，我想将错误从employee repository推送到mvc控制器，如果没有发生错误，则数据将被发送到mvc控制器。这是我的完整代码。请看看并分享最佳设计的想法。如果可能，请在此处修改代码。
public abstract class AdoRepository<T> where T : class
{
private SqlConnection _connection;
public virtual void Status(bool IsError, string strErrMsg)
{
}
public AdoRepository(string connectionString)
{
_connection = new SqlConnection(connectionString);
}
public virtual T PopulateRecord(SqlDataReader reader)
{
return null;
}
public virtual void GetDataCount(int count)
{
}
protected IEnumerable<T> GetRecords(SqlCommand command)
{
var reader = (SqlDataReader) null;
var list = new List<T>();
try
{
command.Connection = _connection;
_connection.Open();
reader = command.ExecuteReader();
while (reader.Read())
{
list.Add(PopulateRecord(reader));
}
reader.NextResult();
if (reader.HasRows)
{
while (reader.Read())
{
GetDataCount(Convert.ToInt32(reader["Count"].ToString()));
}
}
Status(false, "");
}
catch (Exception ex)
{
Status(true, ex.Message);
}
finally
{
// Always call Close when done reading.
reader.Close();
_connection.Close();
_connection.Dispose();
}
return list;
}
protected T GetRecord(SqlCommand command)
{
var reader = (SqlDataReader)null;
T record = null;
try
{
command.Connection = _connection;
_connection.Open();
reader = command.ExecuteReader();
while (reader.Read())
{
record = PopulateRecord(reader);
Status(false, "");
break;
}
}
catch (Exception ex)
{
Status(true, ex.Message);
}
finally
{
reader.Close();
_connection.Close();
_connection.Dispose();
}
return record;
}
protected IEnumerable<T> ExecuteStoredProc(SqlCommand command)
{
var reader = (SqlDataReader)null;
var list = new List<T>();
try
{
command.Connection = _connection;
command.CommandType = CommandType.StoredProcedure;
_connection.Open();
reader = command.ExecuteReader();
while (reader.Read())
{
var record = PopulateRecord(reader);
if (record != null) list.Add(record);
}
}
finally
{
// Always call Close when done reading.
reader.Close();
_connection.Close();
_connection.Dispose();
}
return list;
}
}
StudentRepository which extend base AdoRepository
-----------------------------------------------
public class StudentRepository : AdoRepository<Student>
{
public int DataCounter { get; set; }
public bool hasError { get; set; }
public string ErrorMessage { get; set; }
public StudentRepository(string connectionString)
: base(connectionString)
{
}
public IEnumerable<Student> GetAll()
{
// DBAs across the country are having strokes
// over this next command!
using (var command = new SqlCommand("SELECT ID, FirstName,LastName,IsActive,StateName,CityName FROM vwListStudents"))
{
return GetRecords(command);
}
}
public Student GetById(string id)
{
// PARAMETERIZED QUERIES!
using (var command = new SqlCommand("SELECT ID, FirstName,LastName,IsActive,StateName,CityName FROM vwListStudents WHERE Id = @id"))
{
command.Parameters.Add(new ObjectParameter("id", id));
return GetRecord(command);
}
}
public IEnumerable<Student> GetStudents(int StartIndex, int EndIndex, string sortCol, string sortOrder)
{
string strSQL = "SELECT * FROM vwListStudents WHERE ID >=" + StartIndex + " AND ID <=" + EndIndex;
strSQL += " ORDER BY " + sortCol + " " + sortOrder;
strSQL += ";SELECT COUNT(*) AS Count FROM vwListStudents";
var command = new SqlCommand(strSQL);
return GetRecords(command);
}
public override Student PopulateRecord(SqlDataReader reader)
{
return new Student
{
ID = Convert.ToInt32(reader["ID"].ToString()),
FirstName = reader["FirstName"].ToString(),
LastName = reader["LastName"].ToString(),
IsActive = Convert.ToBoolean(reader["IsActive"]),
StateID = Convert.ToInt32(reader["StateID"].ToString()),
StateName = reader["StateName"].ToString(),
CityID = Convert.ToInt32(reader["CityID"].ToString()),
CityName = reader["CityName"].ToString()
};
}
public override void GetDataCount(int count)
{
DataCounter = count;
}
public override void Status(bool IsError, string strErrMsg)
{
hasError = IsError;
ErrorMessage = strErrMsg;
}
}
public class StudentController : Controller
{
private StudentRepository _data;
public StudentController()
{
_data = new StudentRepository(System.Configuration.ConfigurationManager.ConnectionStrings["StudentDBContext"].ConnectionString);
}
// GET: Stuent
public ActionResult List(StudentListViewModel oSVm)
{
StudentListViewModel SVm = new StudentListViewModel();
SVm.SetUpParams(oSVm);
SVm.Students = _data.GetStudents(SVm.StartIndex, SVm.EndIndex, SVm.sort, oSVm.sortdir).ToList();
SVm.RowCount = _data.DataCounter;
return View("ListStudents",SVm);
}
}
答案 0 :(得分：1)
我不明白这一点：
catch (Exception ex)
{
Status(true, ex.Message);
}
根本没有抓住异常，让它冒泡到打电话人，据你说，他知道要处理它。无需回调。
将检索到的数据存储在实例状态似乎是一种糟糕的方法。而是返回具有该数据的对象。这导致更直接的API并且具有更少的可变状态。
finally
{
reader.Close();
_connection.Close();
_connection.Dispose();
}
有一种更好的方法：在using语句中包装资源。特别是，迷信双重配置模式的部分方式。
答案 1 :(得分：0)
让调用者处理异常，确保您记录一个体面的错误消息（显示所有相关字段）。 Status类会惹恼支持人员，因为它吞下了堆栈跟踪，并且没有说明导致错误的数据。数据库异常通常是由格式错误的数据引起的，因此在出现问题时记录这些数据非常重要。
另外，您的PopulateRecord和GetDataCount方法应该是抽象的，因为基本版本什么都不做。另一个开发人员可能很容易认为他们不需要实现这些方法，并且会留下一个没有无用的PopulateRecord和GetDataCount方法的类。